I agree, for a normal healthy pregnancy, you probably only need to worry about the 20week u/s. If you pay cash, it usually isn't as high as with insurance. {I guess they really want their money}. I am only speaking from my experience though. I think it also has to do with if you have to go to the hospital or if your ob has one in office. Mine was a lot cheaper at the office than the hospital. I think 299 is a good goal, but speaking directly with your doctor's office billing will tell you exactly. You can also opt out of any non necessary things if you want. {That is even with insurance}.
Good Luck mama! Keep us posted! I haven't paid for an u/s in a long time, but will definitely get a 3 or 4d u/s with next pregnancy. Those range in price from 200-400 from what we have found out. Those aren't necessary though, it is just a "want" for me.